One area of automotive vehicle technology that is evolving rapidly is the area of autonomous or semi-autonomous drive capabilities. This is enabled through the introduction of sensors, for sensing vehicle parameters and surroundings, and actuators, for controlling different vehicle functionalities, such as steering, throttling and braking. Increased on-board data processing capabilities ties together these sensors and actuators such that the autonomous or semi-autonomous drive capabilities are enabled.
When the vehicle runs in autonomous mode, which means the driver is not required to perform maneuvers, the vehicle usually is dependent on multiple data sources as inputs to perform the autonomous driving, such as detection of surrounding vehicles, traffic lanes, obstacles, data from navigation systems and so on. Provisions of such inputs are usually dependent on electrical power supplies and signaling systems for enabling the autonomous drive mode. However, should one or more of these inputs not be available, e.g., due to a problem in the electrical power supplies and signaling systems, there might not be sufficient information to perform autonomous driving.
A previously known solution to handle a situation where there is no longer any electrical energy or any fluidic pressure available in an autonomous vehicle owing to a fault is described in US2005029864 (A1).
US2005029864 (A1) relates to a brake system for a vehicle that can be operated without a driver. It has a service brake device, a parking brake device and an emergency braking device. At least the wheel brake devices of the wheels of one axle of the vehicle have emergency brake actuators which switchover the assigned wheel brake devices into the braking state as a result of the triggering of an emergency braking operation. The emergency braking operation can be triggered either manually by means of an emergency operator control device or automatically by means of a monitoring device if the latter has detected an unacceptable operating state of the vehicle in the driverless operating mode. As soon as the monitoring device detects an unacceptable operating state said monitoring device brings about a corresponding triggering signal which triggers the emergency braking operation. Emergency brake actuators are expediently mechanically pre-stressed into a position of rest in such a way that when the emergency brake actuators are in the position of rest the assigned wheel brake devices are in the braking state. The wheel brake devices are capable of being switched over, by acting appropriately on the emergency brake actuators, fluidically and/or electrically between the braking state and an enabling state which enables the assigned wheels of the vehicle. This permits an emergency braking operation to be carried out even if there is no longer any electrical energy or any fluidic pressure available in the vehicle owing to a fault. The emergency brake actuators may be formed by spring brake cylinders.
Thus, the pre-stressed spring brake cylinders according to US2005029864 (A1) will be brought into the position of rest by the springs in such a way that the assigned wheel brake devices are brought into the braking state for performing an emergency braking operation if the monitoring device has detected an unacceptable operating state of the vehicle, such as absence of electrical energy, whilst in the driverless operating mode. Thus it is suggested that the vehicle can be stopped safely and quickly, for example in order to prevent an accident.
However, there is still room for improvements relating to safely bringing an autonomous vehicle to a halt in case of a fault rendering the control systems of the autonomous vehicle unable to perform autonomous driving.